Twelve people have been injured in a knife attack at the main railway station in the German city of Hamburg.

Three of the victims are said to be in critical condition, with three others seriously injured.

Police say they have arrested a 39-year-old woman and a major operation is under way.

The attack is understood to have happened at Hamburg’s Central Station at about 18:00 local time (17:00 BST) on Friday.

A spokesman for the Hamburg fire department told AFP news agency that 12 people had been injured and that some of the injuries were life-threatening.

In a post on X, Hamburg Police said: “According to initial findings, a person allegedly injured several people with a knife in the main station.

“The suspect was arrested by police.”

Police later added that they believe the woman acted alone.

Local media has reported the attack happened near platforms 13 and 14 – which are accessible via a busy main road – while a train was on one of the platforms.

Some of the victims were treated inside trains, according to reports.

Pictures from the scene show a number of emergency service personnel and vehicles on the ground, and barriers that seem to be hiding the injured from public view.

One photograph used by German media shows a man being taken away by paramedics on a stretcher.

A video on social media appears to show the suspect being escorted out of the station platform by officers, with her hands behind her back, and put into a police vehicle.

Hamburg Central Station is one of Germany’s busiest transport hubs, with more than 550,000 travellers per day according to its website. It is often crowded during Friday rush hour.

This is the latest in a series of violent attacks in Germany in recent months.